That's frustrating Western diplomats who continue to push for Assad's ouster as a necessary part of a peace agreement in the Mideast nation's bloody civil war.
Bolstered by infighting among Syrian opposition groups — including some linked to al-Qaida — Assad has a stronger grasp on power now than he did just months ago, U.S. officials say.
How to persuade Assad to step down will be part of the focus Tuesday at a London meeting of 11 nations from the West and Mideast seeking a negotiated settlement to the war.
U.S. Secretary of State John Kerry says Assad's recent gains do not assure his future in a new government.
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